1. Technical Field
The disclosure generally relates to voltage conversion circuits, and more particularly relates to a voltage conversion circuit used in a charging device.
2. Description of the Related Art
Portable electronic devices such as a mobile phone often have a universal serial bus (USB) interface for charging. When a battery of the portable electronic device needs to be charged, a USB cable is connected between the USB interface of the portable electronic device and a USB interface of a computer, then a charge current from the computer can charge the battery through a over voltage protection circuit and a charging circuit. However, due to restrictions of the USB protocol, the charge current is usually no more than 500 mA. Actually, the charge current is only about 450 mA considering a variety of errors. However, charge current can be about 1000 mA by using a traditional mobile phone charger, so charge efficiency is lower by using the USB interface, and users must spend more time charging compared with using a traditional mobile phone charger.
Therefore, there is room for improvement within the art.